Adaptive inductive power supply with communication

ABSTRACT

An adaptive inductive ballast is provided with the capability to communicate with a remote device powered by the ballast. To improve the operation of the ballast, the ballast changes its operating characteristics based upon information received from the remote device. Further, the ballast may provide a path for the remote device to communicate with device other than the adaptive inductive ballast.

This application incorporates by reference the following references:U.S. Pat. No. 7,212,414 to Baarman, which is entitled “AdaptiveInductive Power Supply” and issued May 1, 2007; U.S. Pat. No. 7,132,918to Baarman et al., which is entitled “Inductive Coil Assembly” andissued Nov. 7, 2006; and U.S. Pat. No. 7,518,267 to Baarman, which isentitled “Adapter” and issued Apr. 14, 2009. This application alsoincorporates by reference the full disclosure of the prior applications,including U.S. application Ser. No. 13/078,100 filed Apr. 1, 2011, U.S.Pat. No. 7,953,369 issued May 31, 2011, U.S. Pat. No. 7,522,878 issuedApr. 21, 2009, and U.S. Application No. 60/444,794 filed Feb. 4, 2003.

BACKGROUND OF THE INVENTION

This invention relates generally to contactless power supplies, and morespecifically to contactless power supplies capable of communicating withany devices receiving power from the contactless power supplies.

Contactless energy transmission systems (CEETS) transfers electricalenergy from one device to another without any mechanical connection.Because there is no mechanical connection, CEETS have many advantagesover conventional energy systems. They are generally safer because thereis little danger of sparks or electric shocks due to the isolation ofthe power supply. They also tend to have a longer life since there areno contacts to become worn. Due to these advantages, CEETS have beenused in everything from toothbrushes to portable telephones to trains.

CEETS are composed of power supplies and remote devices. The remotedevice could be chargeable devices such as batteries, micro-capacitors,or any other chargeable energy source. Alternatively, CEETS coulddirectly power the remote devices.

One kind of CEETS uses magnetic induction to transfer energy. Energyfrom a primary winding in the power supply is transferred inductively toa secondary winding in the chargeable device. Because the secondarywinding is physically spaced from the primary winding, the inductivecoupling occurs through the air.

Without a physical connection between the primary winding and thesecondary winding, conventional feedback control is not present. Thus,control of the energy transfer in a CEETS from the primary to thesecondary is difficult.

One common solution is to design a CEETS dedicated to one type ofdevice. For example, a CEETS for a rechargeable toothbrush is designedonly for recharging a toothbrush, while a CEETS for a rechargeabletelephone works only with a specific type of telephone. While thissolution allows the CEET to operate effectively with one particulardevice, it fails to be sufficiently flexible to allow the power supplyto operate with different remote devices.

Further, since the remote device could be an electronic device capableof performing various tasks, communication with the remote device isdesirable. One such system is described in U.S. Pat. No. 6,597,076, inwhich an actuator powered by a CEET communicates with a process computerin order to provide information relating to up-to-date actuatorinformation. The remote device communicates with a transceiver locatedat a central processor. Direct communication between the CEET and theactuator is not, however, provided.

In a system shown in U.S. Pat. No. 5,455,466, a portable electronicdevice receives power from a CEET. Communication between a computer andthe portable electronic device is provided by way of the CEET. The CEETacts as a pipeline between the portable electronic device and thecomputer. The CEET does not obtain information related to the operationof the CEET from the remote device.

While these prior art systems do provide communication, they fail toprovide a method or means for the remote device to supply informationwhich could be helpful to the operation of the CEET. For example, a CEETwith an adjustable power output could use power requirements from theremote device to operate more efficiently by adjusting its power output.Thus, enabling a CEET to communicate with a remote device in order toobtain power requirements from that remote device is highly desirable.

SUMMARY OF THE INVENTION

A contactless power supply has a resonant circuit having a variableresonant frequency and a primary winding for transferring power to aremote device. The contactless power supply also may have a receiver forcommunicating with the remote device. The remote device sends powerinformation to the controller. The controller then modifies theoperation of the resonant circuit in response to the power information.Thus, the controller can precisely calibrate the power supply foroperation with the remote device, providing high efficiency powertransfer from the contactless power supply to the remote device.

The contactless power supply could have an inverter and a power sourcein addition to the resonant circuit coupled to the inverter. In order toachieve high efficiency power transfer, the controller can modify therail voltage of the power supply, the frequency of operation of theinverter, the duty cycle of the inverter as well as the resonantfrequency of the resonant circuit.

The contactless power supply can also be provided with a memory forstoring the power information received from the remote device.

The contactless power supply could also operate with a number of remotedevices. The contactless power supply would then receiver powerinformation from each of the remote devices. A list of the powerinformation for each of the remote devices is maintained. Based upon thelist, the controller determines an optimal settings for the railvoltage, resonant frequency or the duty cycle based upon the list.

The contactless power supply may also have a communication interface forcommunicating with a workstation. The controller would create acommunication link between the workstation and the remote device by wayof a transceiver.

The remote device has a remote device controller and a secondary windinghaving a secondary winding variable impedance. The remote devicecontroller is capable of varying the secondary winding variableimpedance. The remote device has a remote device transceiver forcommunicating with the contactless power supply. The remote devicecontroller varies the secondary winding variable impedance based uponinformation from the contactless power supply. The remote device'scontroller could also disable the operation of the remote device basedupon information from the contactless power supply. Thus, the remotedevice could also be operated at a high efficiency.

Thus, the system allows the optimization of both the power supply aswell as the device attached to the power supply.

The contactless power and remote devices operate by each remote devicesending power usage information to the controller and then adapting thecontactless power supply in response to the power usage information. Theadaptation of the contactless power supply includes changing the dutycycle, the inverter frequency, the resonant frequency, or the railvoltage.

The power supply could also determine whether the contactless powersupply is capable of supplying power to the plurality of remote devices.If not, some of the remote devices could be turned off.

The contactless power supply, the remote device, and the method ofoperating the power supply and the remote device result in an extremelyefficient and very adaptable method of energizing a variety of devicesfrom the power supply. By continually adapting to the addition orremoval of loads to the contactless power supply, the contactless powersupply remains highly efficient.

These and other objects, advantages and features of the invention willbe more readily understood and appreciated by reference to the detaileddescription of the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an adaptive inductive ballast in accordancewith one embodiment of the present invention.

FIG. 2 is a schematic diagram of the resonance-seeking ballast of theattached patent application marked to show changes to incorporate theadaptive inductive ballast of the present invention.

FIG. 3 is a flow chart illustrating operation of the adaptive inductiveballast.

FIG. 4 is a block diagram of an alternative embodiment incorporating RFcommunications and phase control.

FIG. 5 is a flow chart illustrating operation of the adaptive inductiveballast incorporating communications capability

FIG. 6 shows a contactless energy transmission system connected to aremote device and a workstation.

FIG. 7 is a block diagram for an adaptive contactless energytransmission system with communications capability.

FIG. 8 is a block diagram of a remote device with communicationscapability.

FIG. 9 is a flow chart showing the operating of an adaptive contactlessenergy transmission system.

FIG. 10 is an exemplary list of remote devices powered by a contactlesspower supply with communications capability.

DETAILED DESCRIPTION OF THE DRAWINGS

For purposes of disclosure, the present invention is described inconnection with a resonance-seeking ballast circuit, and moreparticularly in connection with the inductive ballast described in U.S.patent application Ser. No. 10/246,155 entitled “Inductively CoupledBallast Circuit,” which is incorporated in its entirety by referenceinto this application. The present invention is, however, well suitedfor use with other inductive ballast circuits.

A block diagram showing the general construction of an adaptiveinductive ballast 10 in accordance with one embodiment of the presentinvention is shown in FIG. 1. As illustrated, the adaptive inductiveballast 10 generally includes a microprocessor 12 that controlsoperation of the circuit, a multi-tap primary 14 for generating amagnetic field, a wave shaper and drive subcircuit 16 that generates thesignal applied to the primary 14, a current sense subcircuit 18 thatmonitors the signal applied to the primary 14 and provides correspondingfeedback to the microprocessor 12, a capacitance switch 20 for adjustingthe capacitance values in the wave shaper and drive subcircuit 16, andan inductance switch 22 for adjusting the inductance of the multi-tapprimary 14. The microprocessor is a conventional microprocessor widelyavailable from a variety of suppliers.

The capacitance switch 20 generally includes two banks of capacitors anda plurality of switches, such as transistors, that are selectivelyactuatable by the microprocessor 12 to control the values of the twocapacitor banks. The capacitors in each bank can be arranged in seriesor parallel depending on the desired range and distribution of possiblecapacitance values. The first bank of capacitors replace capacitor 271.Similarly, the second back of capacitors replace capacitor 272 of thepre-existing resonance-seeking ballast shown in the attached patentapplication. In effect, the capacitance switch 20 makes capacitors 271and 272 from the pre-existing resonance-seeking ballast into variablecapacitors, the values of which are controlled by the microprocessor 12.Alternatively, the described capacitance switch 20 can be replaced byother circuitry capable of providing variable capacitance.

The inductance switch 22 generally includes a multi-tap primary 14 and aplurality of switches, such as transistors, that are selectively actualby the microprocessor 12 to control the values of the inductance of theprimary 14. The multi-tap primary 14 replaces primary 270 of thepre-existing resonance-seeking ballast. In effect, the inductance switch22 makes primary 270 from the pre-existing resonance-seeking ballastinto a variable inductance coil by varying the number of turns in theprimary 14, the value of which is controlled by the microprocessor 12.Alternatively, the described inductance switch 22 can be replaced byother circuitry capable of providing variable inductance.

In general operation, the microprocessor 12 is programmed to receiveinput from the current sense subcircuit 18, which is indicative of thecurrent applied to the primary 14. The microprocessor 12 is programmedto separately adjust the capacitance switch 20 and the inductance switch22 to cycle through the range of capacitance values and inductancevalues available to the circuit. The microprocessor 12 continues tomonitor the input from the current sense circuit 18 while adjusting thecapacitance and inductance values to determine which values provideoptimum current to the primary 14. The microprocessor 12 then locks theadaptive ballast into the optimum settings.

Some of the changes required to adapt the resonance-seeking inductiveballast of the prior patent application into an embodiment of theadaptive inductive ballast circuit 10 are noted in the schematic diagramof FIG. 2.

While the pre-existing resonance-seeking ballast is described in greaterdetail in U.S. patent application Ser. No. 10/246,155, an overview ofthe circuit may be helpful to a fuller understanding of this invention.A ballast feedback circuit is connected at point A and a control circuitis connected at point B. Oscillator 144 provides half bridge inverter148 with an alternating signal by way of drive 146. Half bridge inverterpowers tank circuit 150. Current sensing circuit 218 provides feedbackto oscillator 144. The feedback circuit, control circuit, oscillator,half bridge inverter, drive and current sensing circuit 218 as well asother supporting circuitry is more fully described in the abovereferenced patent application.

In FIG. 2, a phase delay could be inserted at E and can be controlled asa delay line. This delay can be used to throttle the phase and controlsecondary amplitude. At F, switched capacitance can adjust the resonantfrequency based on the adjustable primary inductance. Simple transistorscan be used to switch in and out capacitance. The capacitance is changedwhen the primary inductor changes as to match load. At G, primaryinductance can be switched to adjust the power required by the secondarycircuit. RFID or direct communications can indicate the needed load.With that load information, the control processor can adjust theinductance as needed to provide the power required. The inductance canbe switched using transistors and multiple taps from the primaryinductor controlled by the microprocessor.

The operating sequence of the adaptive inductive ballast circuit isdescribed in more detail in connection with FIG. 3. In operation, theillustrated system waits until it determines that a load is presentbefore applying power to the primary 14. This will save power and may bedone by providing each inductively powered device with a magnet thatactuates a reed switch adjacent to the primary. Alternatively, auser-actuated switch (not shown) may be provided so that the user canengage the power supply when an inductively powered device is present.As another alternative, the inductively powered device may be configuredto mechanically actuate a switch when it is placed into proximity withthe primary to signal its presence. As a further alternative, theswitching mechanism can be eliminated and the ballast circuit canprovide power to the primary 14 regardless of the presence of a load.

Once the power supply circuit is activated, the circuit adjusts itsfrequency to optimize the current applied to the primary. After theappropriate operating frequency has been determined at initialcapacitance and inductance values, the microprocessor locks the ballastcircuit into the operating frequency and then begins to cycle throughthe range of inductance values available through the multi-tap primary.After each change in inductance value, the microprocessor unlocks theoperating frequency and permits the ballast circuit to seek resonance,settling at a frequency that provides optimal current to the primary.The microprocessor continues cycling through the available inductancevalues until it has determined which value provides optimal current tothe primary. In one embodiment, a progressive scanning process is usedto determine the appropriate inductance value. This is achieved bystarting the scanning process with the lowest inductance value, andsequentially stepping up the inductance value until the change ininductance value results in a reduction in the current applied to theprimary. The microprocessor will then step back down one inductancevalue, where the greatest current was achieved. Alternatively, thescanning process may begin with the highest inductance value, andsequentially step down the inductance value until the change ininductance value results in a reduction in the current applied to theprimary. The microprocessor will then step back up one inductance value,where the greatest current was achieved. As another alternative, themicroprocessor can step through each inductance value to determine thecorresponding current, and after stepping through each value, return tothe inductance value that provided the greatest current to the primary.

After the appropriate inductance value is determined, the microprocessorlocks the circuit at the determined inductance value and begins to cyclethrough the capacitance values. In one embodiment, the microprocessoruses a progressive scanning technique to determine the capacitance thatprovides the primary with the greatest current. The scanning process mayprogress upwardly from the lowest capacitance value or downwardly fromthe highest capacitance value, as described above in connection with thescanning process for the inductance value. As an alternative to aprogressive scanning process, the microprocessor can step through eachcapacitance value to determine the corresponding current, and afterstepping through each value, return to the capacitance value thatprovided the greatest current to the primary.

In this embodiment, the frequency of the ballast circuit is notpermitted to vary once the appropriate inductance value has beendetermined. The microprocessor can, alternatively, be programmed topermit the ballast circuit to seek resonance after each change incapacitance value.

In an alternative embodiment, the microprocessor may be programmed toprovide adjustment of only the capacitance value or only the inductancevalue of the power supply circuit. In the former alternative, themulti-tap primary can be replaced by a conventional single-tap primaryand the inductance switch can be eliminated. In the latter alternative,the capacitor bank can be replaced by a single set of capacitors and thecapacitance switch can be eliminated. In another alternative embodiment,the microprocessor can be programmed to adjust the capacitance beforeadjusting the inductance.

As noted above, the present invention is not limited to use inconnection with a resonance-seeking ballast. In other applications, acurrent sensor may be incorporated into the ballast to provide input tothe microprocessor that is representative of the current being appliedto the primary. In operation without a resonance-seeking ballast, themicroprocessor will separately cycle through the various capacitance andinductance values to determine the values that provide optimum power tothe primary.

In a further alternative embodiment, the adaptive inductive ballast 10may include phase delay circuitry (not shown) that permits the ballast10 to throttle the phase and control secondary amplitude. The phasedelay circuitry may include a delay line or a Digital Signal Processor(DSP) that is connected to the wave shaper and drive circuit 16following the operational amplifier 210.

A further alternative embodiment of the present invention is describedin connection with FIGS. 4-5. In this embodiment, the adaptive inductiveballast 10′ and the inductively powered device have the ability tocommunicate, for example, using conventional RF communications or directcommunications.

FIG. 4 is a block diagram showing the general components of the adaptiveinductive ballast 10′. The adaptive inductive ballast 10′ includes acommunication coil (not shown) that is separate from the switchedprimary inductance and primary coil 22′. The communication coil could bepart of the primary. The communication coil is connected to themicroprocessor 12′, which is programmed to receive the information fromthe inductively powered device and to effect operation of the adaptiveinductive ballast 10′ based on that information. The inductively powereddevice also includes a communication coil that could be separate from orintegral with the secondary that receives power from the primary. Theinductively powered load and the adaptive inductive power supply 10′communicate using conventional communications techniques and apparatus,for example, using standard communications circuitry and standardcommunications protocol.

Operation of the adaptive ballast 10′ is generally identical to that ofballast 10 described above, except as noted below. A flow chart showingthe general steps of operation of the ballast 10′ is show in FIG. 5.Through the use of its communications capability, the inductivelypowered device can relay load information to the adaptive inductiveballast 10′, such as the wattage of the load. The adaptive inductiveballast 10′ can use this information in determining the appropriatecapacitance and inductance values. More specifically, this informationcan be used to ensure that the primary of switched primary inductanceand primary coil 22′ is operating at the correct wattage. If not, theswitched primary inductance of switched primary inductance and primarycoil 22′ and capacitance switch 20′ can be used to adjust the wattage ofthe primary. This embodiment may, in some applications, provide improvedoperation over adaptive inductive ballast 10 described above because itdoes not necessarily drive the primary at its highest possible currentvalue. Instead, this embodiment matches the power output of the primaryto the power requirements of the inductively powered device, meaningthat it may reduce power and save energy when full power is notrequired.

The aforementioned system of FIGS. 1-5 is further enhanced and explainedwith reference to FIGS. 6-9.

FIG. 6 shows an adaptive contactless energy transmission systemincorporating one embodiment of the present invention. Contactless powersupply 305 is inductively coupled to remote device 306. Contactlesspower supply 305 is also connected to workstation 307. Network 308 is,in turn, connected to workstation 307.

In one embodiment, contactless power supply 305 establishes acommunication link between workstation 307 and remote device 306,allowing information to be transmitted to and from remote device 306. Ifremote device 306 were a PDA (personal digital assistant), informationfrom the PDA could be exchanged with workstation 307. For example, a PDAcould automatically synchronize a calendar and an address list while thePDA was charging. As another example, if remote device 306 were an MP3player, then songs could be downloaded to and from the MP3 player whilethe MP3 player was charging.

FIG. 7 shows a block diagram for an embodiment of an adaptivecontactless energy transmission system with communication forcommunicating with a plurality of remote devices.

The adaptive contactless energy transmission system has contactlesspower supply 305 and remote device 338, 340, 342.

As is well know, power source 310 is a DC power source providing DC(direct current) power to inverter 312. Inverter 312 converts the DCpower to AC (alternating current) power. Inverter 312 acts as an ACpower source supplying the AC power to tank circuit 314. Tank circuit314 is a resonant circuit. Tank circuit 314 is inductively coupled tosecondary winding 316 of remote device 338.

The secondary windings of remote devices 338, 340, 342 have no core.Dashed line 320 indicates an air gap between remote devices 338, 340,342 and power supply 305.

Circuit sensor 324 is coupled to the output of tank circuit 314. Circuitsensor 324 is also coupled to controller 326. Circuit sensor 324provides information regarding the operational parameters of the powersupply. For example, circuit sensor could be a current sensor andprovide information regarding the phase, frequency and amplitude of thecurrent in tank circuit 314.

Controller 326 could be any one of a multitude of commonly availablemicrocontrollers programmed to perform the functions hereinafterdescribed, such as the Intel 8051 or the Motorola 6811, or any of themany variants of those microcontrollers. Controller 326 could have a ROM(read only memory) and RAM (random access memory) on the chip.Controller 326 could have a series of analog and digital outputs forcontrolling the various functions within the adaptive inductive powersupply.

Controller 326 is connected to memory 327. Controller 326 is alsocoupled to drive circuit 328. Drive circuit 328 regulates the operationof inverter 312. Drive circuit 328 regulates the frequency and timing ofinverter 312. Controller 326 is also coupled to power source 310.Controller 326 can manipulate the rail voltage of power source 310. Asis well known, by altering the rail voltage of power source 310, theamplitude of the output of inverter 312 is also altered.

Finally, controller 326 is coupled to variable inductor 330 and variablecapacitor 332 of tank circuit 314. Controller 326 can modify theinductance of variable inductor 330 or the capacitance of variablecapacitor 332. By modifying the inductance of variable inductor 330 andthe capacitance of variable capacitor 332, the resonant frequency oftank circuit 314 can be changed.

Tank circuit 314 could have a first resonant frequency and a secondresonant frequency. Tank circuit 314 could also have several resonantfrequencies. As used herein, the term “resonant frequency” refers to aband of frequencies within which tank circuit 314 will resonate. As iswell known, a tank circuit will have a resonant frequency, but willcontinue to resonate within a range of frequencies. Tank circuit 314 hasat least one variable impedance element having a variable impedance. Byvarying the variable impedance, the resonant frequency of the tankcircuit will be varied. The variable impedance element could be variableinductor 330 or variable capacitor 332, or both.

Variable inductor 330 could be a thyristor controlled variable inductor,a compressible variable inductor, parallel laminated core variableinductor, a series of inductors and switches capable of placing selectfixed inductors into tank circuit 314, or any other controllablevariable inductor. Variable capacitor could be a switched capacitorarray, a series of fixed capacitors and switches capable of placingselect fixed capacitors into tank circuit 314, or any other controllablevariable capacitor.

Tank circuit 314 also includes primary winding 334. Primary winding 334and variable inductor 330 are shown separate. Alternatively, primarywinding 334 and variable inductor 330 could be combined into a singleelement. Tank circuit 314 is shown as a series resonant tank circuit. Aparallel resonant tank circuit could also be used.

Power supply transceiver 336 is also coupled to controller. Power supplytransceiver 336 could be simply a receiver for receiving informationrather than a device enabling two-way communication. Power supplytransceiver 336 communicates with various remote device 338, 340, 342.Obviously, more or less devices than three could be used with thesystem.

In this embodiment, contactless power supply 305 also has communicationinterface 311 for connection to workstation 307. Communication interface311 could be any of a number of well known or proprietary interfacessuch as USB, firewire, or RS-232. Workstation 307 is connected tonetwork 308. Network 308 could be a LAN (local area network) or theInternet.

Contactless power supply 305 could also have communication controller313. Communication controller 313 manages data input and output throughcommunication interface 311 and power supply transceiver 336.Communication controller 313 performs necessary control functions suchas code conversion, protocol conversion, buffering, data compression,error checking, synchronization and route selection as well as collectsmanagement information. Communication controller 313 establishescommunication sessions between remote devices 338, 340, 342 andworkstation 307 or any other devices within network 308. Communicationcontroller 313 could be a front end processor. Depending upon thecapabilities of controller 326, communication controller 313 could be asoftware module running within controller 326.

FIG. 8 shows a block diagram of remote device 338. Remote device 338 isexemplary of remote devices 340, 342 as well. Remote device 338 includesload 350. Load 350 receives power from variable secondary 353. Load 350could be a rechargeable battery or any other kind of load.

Variable secondary 353 is preferably coreless, allowing variablesecondary 353 to operate over a wider range of frequencies. Variablesecondary 353 is shown as a variable inductor, although other types ofdevices could be used in place of the variable inductor.

Remote device controller 352 controls the inductance of variablesecondary 353 and the operation of load 350. For example, remote devicecontroller 352 can alter the inductance of variable secondary 353 orturn on or off load 350. Similar to controller 326, remote devicecontroller 352 could be any one of a multitude of commonly availablemicrocontrollers programmed to perform the functions hereinafterdescribed, such as the Intel 8051 or the Motorola 6811, or any of themany variants of those microcontrollers. Controller 352 could have a ROM(read only memory) and RAM (random access memory) on the chip.Controller 352 could also have a series of analog and digital outputsfor controlling the various functions within the adaptive inductivepower supply.

Memory 354 contains, among other things, a device ID (identification)number and power information about remote device 338. Power informationwould include the voltage, current and power consumption information forremote device 338. If load 350 were a rechargeable battery, memory 354might include discharge rates and charging rates.

Remote device 338 also includes remote transceiver 356. Remotetransceiver 356 receives and transmits information to and from powersupply transceiver 336. Remote transceiver 356 and power supplytransceiver 336 could be linked in a myriad of different ways, such asWIFI, infrared, blue tooth, or cellular. Additionally, the transceiverscould communicate by way of additional coils on the primary orsecondary. Or, since power in being delivered by power supply 305 toremote devices 338, 340, 342, by any one of many different power linecommunication systems.

Alternatively, remote transceiver 356 could be simply a wirelesstransmitter for sending information to transceiver 336. For example,remote transceiver 356 could be an RFID (Radio Frequency Identification)tag.

Processor 357 represents the functional component of remote device 338.For example, if remote device 338 were a digital camera, processor 357could be a microprocessor within the digital camera. If remote device338 were an MP3 player, processor 357 could be a digital signalprocessor or a microprocessor and related circuitry for converting MP3files into sounds. If remote device 338 were a PDA, then processor 357would be a microprocessor and related circuitry providing thefunctionality of a PDA. Processor 357 could access memory 354.

Processor 357 is also coupled to secondary device transceiver 356. Thus,processor 357 could communicate through secondary device transceiver 356with contactless power supply 305, and thereby could communicate withany other devices connected to power supply 305, such as a workstation.

Due to the presence of communication interface 311, remote device 338could communicate to workstation 307 or the network 308. In order toenable communication between remote device 338 and workstation 307,controller 326 would establish a communication link to remote device 338by way of transceiver 336.

FIG. 9 shows the operation of the adaptive contactless energytransmission system with communications capability.

After contactless power supply 305 starts (Step 400), it polls allremote devices by way of transceiver 336. Step 402. Step 402 could becontinuous, where advancement to Step 404 occurs only if a remote deviceis present. Alternatively, the following steps could be performed beforepolling is repeated, although the operations would be performed withreference to a null set. If any remote device is present, it receivespower usage information from the remote device. Step 404.

The power usage information could include actual information regardingvoltage, current, and power requirements for remote device 338.Alternatively, power usage information could be simply an ID number forremote device 338. If so, controller 326 would receive the ID number andlook up the power requirement for remote device 338 from a tablecontained in memory 327.

After all devices have been polled and the power information for eachdevice has been received, contactless power supply 305 then determineswhether any device is no longer present. If so, then a remote devicelist is updated. Step 408.

The remote device list maintained by controller 326 is shown in FIG. 10.The remote device list could contain for a device ID, a voltage, acurrent, and a status for each remote device 338, 340, 342. The devicenumber is assigned by controller 326. The device ID is received fromremote devices 338, 340, 342. If two remote devices are the same type,then the device ID could be the same. The voltage and current are theamount of voltage or current required to power the device. The voltageand current could be transmitted discretely by remote devices 338, 340,342, or they could be obtained by using the device ID as a key to adatabase of remote devices maintained in memory 327. The status is thecurrent status of the device. For example, the device status could be‘on’, ‘off’, ‘charging’, etc.

Next, contactless power supply 305 determines whether the status of anydevice has changed. Step 410. For example, remote device 338 could havea rechargeable battery. When the rechargeable battery is fully charged,remote device 338 would no longer need power. Thus, its status wouldchange from “Charging” to “Off.” If the status of the device changes,then the remote device list is updated. Step 412.

Contactless power supply 305 then determines if any devices are present.Step 414. If so, then the remote device list is updated. Step 416. Theremote device list is then checked. Step 418. If the list was notupdated, the system then polls the devices again, and the processrestarts. Step 402.

If the list was updated, then the power usage by the remote devices haschanged, and thus the power supplied by contactless power supply 305must also change. Controller 326 uses the remote device list todetermine the power requirements of all the remote devices. It thendetermines if the system can be reconfigured to adequately power all thedevices. Step 420.

If contactless power supply 305 can supply power to all of the remotedevices, then controller 326 calculates the settings for inverterfrequency, duty cycle, resonant frequency, and rail voltage. Further,controller determines the best setting for the variable impedance ofsecondary winding 353 of remote devices 338, 340, 342. Step 422. It thensets the inverter frequency, duty cycle, resonant frequency, and railvoltage. Step 424. It also instructs remote devices 338, 340, 342 to setthe variable impedance of secondary winding 353 to the desired level.Step 424.

On the other hand, if contactless power supply 305 cannot supply powerto all of the remote devices, controller 326 determines the bestpossible power settings for the entire system. Step 426. It may theninstruct one or more of remote devices 338, 340, 342 to turn off orchange its power consumption. Controller determines the best setting forthe variable impedance of secondary winding 353 of remote devices 338,340, 342. Step 428. It then sets the inverter frequency, duty cycle,resonant frequency, and rail voltage for the system. Step 430.Controller instructs remote devices 338, 340, 342 to set the variableimpedance of secondary winding 353 at the desired level. The system thenreturns to polling the devices, and the process repeats. Step 402.

The above description is of the preferred embodiment. Variousalterations and changes can be made without departing from the spiritand broader aspects of the invention as defined in the appended claims,which are to be interpreted in accordance with the principles of patentlaw including the doctrine of equivalents. Any references to claimelements in the singular, for example, using the articles “a,” “an,”“the,” or “said,” is not to be construed as limiting the element to thesingular.

1. A method for controlling operation of an inductive power supplysystem, comprising the steps of: establishing an inductive couplingbetween the inductive power supply and a remote device having asecondary inductor in electrical communication with a load, theinductive power supply having a controller and a tank circuit; receivinginformation from the remote device; adaptively adjusting a variableimpedance element of the inductive power supply when the remote deviceis inductively coupled with the inductive power supply; adjusting anoperating frequency of the inductive power supply, wherein adjusting theoperating frequency of the inductive power supply includes adjusting adrive circuit with the controller; detecting an operating parameter ofthe tank circuit; and determining whether an operational parameter ofthe tank circuit in the inductive power supply is within a nominalrange, wherein said adjusting is in response to determining that saidoperational parameter is not within the nominal range.
 2. The method ofclaim 1 wherein said adaptively adjusting a variable impedance elementincludes adjusting a resonant frequency of the tank circuit.
 3. Themethod of claim 1 wherein said adjusting a variable impedance elementincludes adjusting with the controller at least one of a variablecapacitance or a variable inductance of the tank circuit.
 4. The methodof claim 1 further comprising adjusting a power level of the inductivepower supply.
 5. The method of claim 1 further comprising establishingan inductive coupling between the inductive power supply and a pluralityof remote devices having a secondary inductor.
 6. The method of claim 1wherein said adjusting an operating frequency includes adjusting theoperating frequency in response to a feedback signal.
 7. The method ofclaim 1 wherein said adjusting an operating frequency includes adjustingthe operating frequency based on the received information from theremote device.
 8. The method of claim 1 further comprising repeatingsaid step of actively adjusting at least one of an operating frequencyof the inductive power supply.
 9. An inductive power supply forsupplying power to a remote device, said inductive power supplycomprising: a primary configured to transfer power to said remote devicea receiver for receiving information from said remote device; acontroller in communication with said primary, said controllerprogrammed to: adaptively adjust a variable impedance element of saidinductive power supply when said remote device is inductively coupledwith said inductive power supply; adjust an operating frequency of saidinductive power supply; detect an operating parameter of said primary;and determine whether an operational parameter of said primary in saidinductive power supply is within a nominal range, wherein said operatingfrequency is adjusted in response to a determination that saidoperational parameter is not within said nominal range.
 10. Theinductive power supply of claim 9 wherein a resonant frequency of saidtank circuit is changed in response to an adjustment of said variableimpedance element.
 11. The inductive power supply of claim 9 whereinsaid controller is programmed to adjust the operating frequency based onthe received information from the remote device.
 12. The inductive powersupply of claim 9 wherein said receiver receives information from saidremote device via an inductive coupling between said primary and saidremote device.
 13. The inductive power supply of claim 9 furtherincluding a tank circuit having said primary, and wherein said variableimpedance element is at least one of a variable capacitance or avariable inductance of said tank circuit.
 14. The inductive power supplyof claim 9 wherein said controller is programmed to adjust a power levelof said inductive power supply.
 15. The inductive power supply of claim9 wherein said inductive power supply supplies power to a plurality ofremote devices.
 16. The inductive power supply of claim 9 wherein saidcontroller adjusts said operating frequency in response to a feedbacksignal.
 17. The inductive power supply of claim 9 wherein saidcontroller is programmed to repeatedly adjust said operating frequencyof said inductive power supply.